A cellular communication system is exemplary of a radio communication system. Cellular communication systems, generally, provide for voice and data communication services. Multiple access by significant numbers of users is permitted in a cellular communication system. Cellular communication systems are popularly utilized and have achieved high levels of penetration in many areas. The network infrastructures of cellular communication systems have been deployed throughout significant portions of the populated areas of the world. Successive generations of cellular communication systems have been developed and deployed, sometimes overlayed upon one another over common geographical areas.
A GSM (Global System for Mobile communications) cellular communication system is representative of a cellular communication system that provides for voice and data services. Operational parameters of equipment operable in a GSM system are set forth in an operational specification promulgated by the EIA/TIA. Enhancements to the initially-deployed GSM system provide, amongst other things, for more extensive data services. An operational specification related to GPRS (General Packet Radio Service) for GSM has also been promulgated, and equipment that provides for GPRS communication services operate pursuant to the parameters set forth in the operational specification of the GPRS system.
Amongst other facets, the operational specification of the GSM/GPRS system defines signaling parameters by which various control, and other, signaling is effectuated during operation of the GSM/GPRS communication system. Because communications are regularly effectuated upon channels susceptible to fading, and other distortion, the operational specification of the system provides for encoding of data in manners to combat the effects of fading. Version 8.4 of the GSM specification includes sections GSM 05.02 relating to multiplexing and multiple access on the radio path and GSM 05.03 related to channel coding. Data bursts are further defined are further defined by a burst-type, such as a normal burst (NB), as described in the GSM 05.02, section 5.2.3. GSM and GPRS packet traffic is passed in bursts of the burst-type of normal burst.
GSM non-voice data is passed in channel types CCCH (Common Control Channel), SDCCH (Standalone Dedicated Control Channel), and SACCH (Slow Associated Control Channel). The encoding techniques, for data transmission, for these three channel types are identical. And, details associated with the encoding parameters are set forth in the GSM specification 05.03, section 4.1. This section specifies the encoding comprising block coding, convolutional encoding, interleaving, and mapping of encoded data onto a burst. The block code computes a forty bit, cyclic redundancy check (CRC) that is appended to 184 bits of data that are encoded in the block. The forty bits are designed to have maximum dependency on other bits in the block.
The convolutional code doubles the number of bits, and composes the new bits such that each of the new bits is to be based on three or four of the data bits from a previous step, i.e., data bits plus bits from the block code. The doubling of the number of bits adds to the redundancy of the data. A Viterbi algorithm is utilized to decode the convolutionally-encoded data. The Viterbi algorithm is able to decode the original data bits even if a substantial number of the bits have been inverted.
After convolutional encoding, the data block is interleaved so that consecutive bits end up in different positions on data bursts that are to be transmitted. And, four data bursts are transmitted to transmit the entire, encoded block. Bit errors are, many times, near each other in clusters of bit errors. By performing interleaving before transmitting, consecutive bits that are corrupted are spread out again by deinterleaving. This is done as the convolutional code is better at dealing with bit errors that are spread out than clustered errors that are clustered theretogether.
Subsequent to transmission and reception, decoding is performed. Decoding operations are performed in a manner reverse to that of the just-described encoding procedures. That is, first, the bits are de-interleaved from the bursts. Subsequently, Viterbi decoding is performed to reverse the convolutional encoding. The Viterbi algorithm that is executed to perform the Viterbi decoding relies upon redundancy in the convolutionally encoded data to detect and correct for corrupted bits, provided that only a relatively small number of bits have been inverted, i.e., corrupted. When the block is again decoded, the calculation is repeated to ensure that the forty bits computed from the 184 received data bits match the forty bits that were sent. If some of the data was incorrectly received, and not successfully corrected, the probability of the forty bits of the CRC forming a match is quite small. And, when erroneous data is received, the data is discarded.
GPRS packet data encoding is similar to encoding of packets in GSM. Several coding schemes are set forth in GPRS. A coding scheme (CS) 1 is identical to a corresponding scheme used in GSM, while coding schemes 2 and 3 also add puncturing, as per GSM 05.03, section 5. Coding scheme 4 has no error correction and omits the convolutional code.
Conventional decoding of a data block is performed subsequent to reception of four bursts that include all of the data of the encoded data block. Burst decoding is done on each burst. Once burst decoding is done, block decoding is performed on the blocks. Conventionally, bits are extracted from the bursts, then deinterleaving is performed, decoding of the convolutional code through execution of a Viterbi algorithm is performed, and the block code is verified.
When the mobile station is operated in an idle mode, or during a packet transfer mode, repetitive data blocks are communicated to the mobile station. Monitoring by the mobile station of each data block is power-consumptive, consuming the limited stored energy of a portable power supply that typically powers the mobile station.
If a manner could be provided by which to exploit the properties of the coding schemes by which a data block is encoded, thereby to reduce the need to monitor all of the encoded data blocks, improved power reception optimization would be provided.
It is in light of this background information related to the communication of encoded data in a radio, or other, communication system that the significant improvements of the present invention have evolved.